The present invention relates to an apparatus for dispensing liquids such as herbicides and insecticides.
Contact herbicides have hitherto been applied to plantlife such as bushes and scrub in large quantity at low to medium concentration, usually in the form of spray delivered by a vehicle-mounted spraying apparatus. More inaccessible areas were reached by an operator carrying a backpack sprayer unit, and again the spray was liberally applied, reliance being placed upon the thorough wetting of the leaves to ensure absorption. Such herbicides are inactive upon soil, and depend for their effectiveness upon translocation from the leaf system to the root system.
Although various devices have been proposed for facilitating the charging and dispensing of liquid carriers, none of these attempts have provided a reliable and portable apparatus for dispensing a controllable amount of liquid at constant pressure for prolonged periods of time.
Many previous attempts combine the propellent gas with the liquid being dispensed, or charge the liquid under pressure prior to entry or inside the device, before spraying same. U.S. Pat. No. 3,353,537 to Knox et al discloses an inoculating instrument which, although overcoming the specific above-referenced problems, has itself several drawbacks which are obviated by the present invention.
U.S. Pat. No. 3,353,537 to Knox et al, discloses a high-speed inoculating or vaccinating instrument specifically for use on chickens and other fowl. The Knox device is therefore adapted for an extremely different field, that is, for high speed and very small dosage dispensing of a vaccine trough a needle. The device requires the use of an air compressor to provide the motive power, and dispenses a predetermined volume of liquid depending on the position of a master piston which must be screw-adjusted. The Knox device is considerably complex in construction, requiring a two-part piston with twin seals. The device as claimed and illustrated is cumbersome to operate and utilise as it stands, and even if it were desirous to increase the dimensions and capabilities of the Knox device to meet the operating characteristics of the present invention, such action would render the Knox device ungainly and unusable in a modified form. Further still, the Knox device requires the use of an air compressor, and therefore could not be provided as a portable unit for use in the field. Due to the provision of the threaded limit device at the rear of the Knox gun, the gun is restricted on its rearward stroke. That is, only a specified individual dosage may be dispensed, as opposed to a variable-sized dosage.
These and other disadvantages are obviated by the present invention which provides a light weight, portable dosing apparatus for applying liquid reagents in agricultural areas. Certain factors emerge as important in devising such an apparatus, including firstly, that herbicides and insecticides must be applied at an effective dosage level. Then the concentration and the area to which it is applied must be predetermined. Secondly, the apparatus is likely to be required in inaccessible places, so that portability is desirable. Thirdly as ejecting liquid by arm or hand operation is tiring when repeated, some form of preferred ejection is advisable. Fourthly it is useful to meter the liquid in discrete doses so that the sprayer may keep in mind the cost of the reagent.
The present invention provides a spraying and dosing apparatus for administering a reagent in a liquid carrier as a spray comprising:
a portable backpack structure moulded of plastics material and provided with: PA1 a metering device comprising a cylinder having a piston movable therein, the piston and cylinder together forming an expansible chamber, spray nozzle means connected to said chamber for delivering a spray of liquid therefrom upon movement of the piston in a direction to contract said chamber, first check valve means connected between said chamber and said spray nozzle means for preventing flow of air into the chamber through said spray nozzle means upon expansion of said chamber, conduit means connected to deliver liquid from said reservoir of said portable backpack structure into said chamber, second check valve means in said conduit means for preventing flow of liquid from said chamber back to said reservoir upon contraction of the chamber, means, operable by the energy of said liquid petroleum gas in said propellant vessel, for moving said piston in a direction to cause said chamber to expand, thereby drawing said liquid from said reservoir of said portable backpack structure into said chamber, means operable by the pressure of said liquid petroleum gas in said propellant vessel for moving said piston in a direction to cause said chamber to contract, and manually operable valve means connected to deliver said liquid petroleum gas under pressure from said propellant vessel to said means operable by the pressure of said liquified gas; PA1 whereby said valve means controls the flow of pressurized liquid petroleum gas, and said dosing apparatus utilizes said liquid petroleum gas pressure to eject said liquid from said chamber, the propellant liquid petroleum gas and the liquid to be sprayed remaining separate.
a reservoir adapted to contain a liquid comprising a reagent in a liquid carrier; PA2 a removable propellant vessel containing liquid petroleum gas under pressure; PA2 a regulator device adapted to said removable vessel to maintain said liquid petroleum gas at substantially constant pressure; and
The metering device may be a dosing gun comprising a piston and cylinder supported on a handle, the cylinder having on one side of the piston a liquid inlet which is connectable to a reservoir of liquid and an outlet which leads to a spray head and a further inlet in the opposite side of the piston which is connectable to a source of pressurized propellant via a control valve.
In a preferred embodiment the piston is spring-biased to the charge position, and a piston rod extends out of the cylinder and carries an adjustable stop so the dose can be altered. The valve is incorporated as a trigger. The pressurized propellant is provided as a cylinder of liquified gas, for example LP gas, or industrial compressed air and the reagent is supplied from a reservoir, these two supplies being incorporated in a backpack. A handle for the gun is not essential but increases the comfort of use of the device.